Nanodevice arrays for electrical energy storage, capture and management and method for their formation

ABSTRACT

An apparatus, system, and method are provided for a vertical two-terminal nanotube device configured to capture and generate energy, to store electrical energy, and to integrate these functions with power management circuitry. The vertical nanotube device can include a column disposed in an anodic oxide material extending from a first distal end of the anodic oxide material to a second distal end of the anodic oxide material. Further, the vertical nanotube device can include a first material disposed within the column, a second material disposed within the column, and a third material disposed between the first material and the second material. The first material fills the first distal end of the column and extends to the second distal end of the column along inner walls of the column. The second material fills the first distal end of the column and extends to the second distal end of the column within the first material. Both the first material and the second material are exposed at the first distal end of the column.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) of U.S.Provisional Patent Application Ser. No. 61/237,155, filed on Aug. 26,2009. The subject matter of the earlier filed application is herebyincorporated by reference.

This invention was made with United States Government support underContract No. H9823004C0448 awarded by the National Security Agency andunder Contract No. DMR0520471 awarded by the National ScienceFoundation. The United States Government has certain rights in thisinvention.

BACKGROUND

1. Field

Embodiments of the invention relate to an apparatus, system, and methodfor nanostructure-based devices for electrical energy management. Moreparticularly, embodiments of the invention relate to an apparatus,system, and method for providing nanostructure arrays as two-terminaldevices, for example, nanotube or nanowire devices (hereinafter referredto as “nanodevices”), configured to store electrical energy, to captureand generate energy, and to integrate with power management circuitry.

2. Description of the Related Art

The limitations of conventional capacitor and battery devices are wellknown. Charge storage devices can exhibit similar limitationsexperienced by conventional solar cell devices, as will be discussedbelow. Electrostatic capacitors that store charge at the surface ofelectrodes typically do not achieve high areal densities of theelectrodes. Electrochemical supercapacitors and batteries that storecharge inside their active surfaces and at the surface also canexperience similar limitations experienced by conventional solar celldevices, as will be discussed below. While sub-surface charge storagecan enhance energy density, the resulting slow ion/charge transport intothese materials can limit available power.

The limitations of conventional devices for energy capture and storageare also well known. In semiconductor pn junction solar cells, planardevice layers typically create only a single depletion layer over thesurface to separate photo-induced carriers. As a result, each substrateof a semiconductor pn junction solar cell can be limited to only asingle active layer. Furthermore, some of the semiconductor material canabsorb light, producing excitations outside a depletion range. This canprevent the separation of positive and negative charges and thecollection of harvested light energy.

Currently, alternate solar cell structures are being explored thatutilize nanocomposite structures that mix nanoparticles, such as C-60 orcarbon nanotubes, with organic materials having random spatialdistributions on a nanoscale. These nanocomposite structures can providea high density of interfaces between the component materials,effectively enhancing the active regions, analogous to depletion regionsin pn junction semiconductor structures, where charge separation canoccur.

However, the nanoscale randomness of the component materials can impedeefficient collection of charges at micro- or macro-scale externalcontacts where charge should be produced, for example, through highelectrical resistance through which the charge reaches the contacts.Additionally, these materials, such as conducting polymers, can haverelatively high resistivity, further diminishing the efficiency ofcharge collection at the external contacts.

A number of nanostructures have been explored to improve the power andenergy density of conventional capacitor and battery devices andconventional solar cell devices, primarily exploiting higher surfacearea densities per unit volume of material used in these devices. Forexample, a high density of nanowires on a surface can substantiallyenhance the surface area available, producing higher charge density perunit planar area. Furthermore, nanowire and nanotube structures canpresent shortened pathways for ion transport into the surface, therebyincreasing power density. These advancements in technology promiseimprovements in energy devices, particularly if nanostructures can beformed with sufficient control at the nanoscale to realize functioningand reliable aggregation of massive arrays of nanostructures into largerworking devices addressed at the macro- or micro-scale externalcontacts.

Nanotechnology provides new options for meeting these requirements,particularly using self-assembly phenomena and self-alignment to buildmore complex nanodevices from simpler nanostructures. For example,anodic aluminum oxide (AAO) can achieve highly regular arrays ofnanopores through specific recipes for anodic oxidation of aluminum.Nanopores in AAO may have uniform size and spacing in a hexagonalpattern.

SUMMARY

In accordance with an embodiment of the invention, there is provided avertical nanotube device, which includes a substrate, and an anodicoxide material disposed on the substrate. The vertical nanotube devicecan further include a column disposed in the anodic oxide materialextending from a first distal end of the anodic oxide material to asecond distal end of the anodic oxide material. Further, the verticalnanotube device can include a first material disposed within the column,a second material disposed within the column, and a third materialdisposed between the first material and the second material. The firstmaterial fills the first distal end of the column and extends to thesecond distal end of the column along inner walls of the column. Thesecond material fills the first distal end of the column and extends tothe second distal end of the column within the first material. Both thefirst material and the second material are exposed at the first distalend of the column.

In accordance with an embodiment of the invention, there is provided avertical two-terminal nanotube device, which includes a column disposedin an anodic oxide material extending from a first distal end of theanodic oxide material to a second distal end of the anodic oxidematerial. The vertical two-terminal nanotube device further includes afirst material disposed within the column, a second material disposedwithin the column, and a third material disposed between the firstmaterial and the second material. The first material fills the firstdistal end of the column and extends to the second distal end of thecolumn along inner walls of the column. The second material fills thefirst distal end of the column and extends to the second distal end ofthe column within the first material. The first material is exposed atthe first distal end of the column, and the second material is exposedat the second distal end of the column.

In accordance with an embodiment of the invention, there is provided avertical two-terminal nanotube device, which includes a plurality ofcolumns, each column disposed in an anodic oxide material extending froma first distal end of the anodic oxide material to a second distal endof the anodic oxide material. The vertical two-terminal nanotube devicefurther includes a first material disposed within the column, a secondmaterial disposed within the column, and a third material disposedbetween the first material and the second material. The first materialfills the first distal end of the column and extends to the seconddistal end of the column along inner walls of the column. The secondmaterial fills the first distal end of the column and extends to thesecond distal end of the column within the first material. The firstmaterial is exposed at the first distal end of the column, and thesecond material is exposed at the second distal end of the column. Theplurality of columns are connected in parallel by a first wiringstructure operatively connected to an exposed end of the first material,and a second wiring structure operatively connected to an exposed end ofthe second material. The first and the second wiring structures areconfigured on a top surface and a bottom surface of the column,respectively.

In accordance with an embodiment of the invention, there is provided avertical two-terminal nanotube device, which includes apressure-controlled vessel. The vessel includes a plurality of columns.Each column is disposed in an anodic oxide material extending from afirst distal end of the anodic oxide material to a second distal end ofthe anodic oxide material. The vessel further includes a materialdisposed within the column. The material includes a chemical sensingfilm. The vessel further includes a first wiring structure operativelyconnected to a top surface of the plurality of columns, and a secondwiring structure operatively connected to a bottom surface of theplurality of columns. The first and the second wiring structures areconfigured on a top surface and a bottom surface of the column,respectively. The pressure-controlled vessel is configured to allow agas or liquid to flow through the plurality of columns. The first andsecond wiring structures are configured to measure a resistance changebased on an adsorption, absorption or reaction of species from the gasor liquid on the material.

In accordance with an embodiment of the invention, there is provided amethod, which includes the step of forming a columnar pore in an exposedportion of a material layer, depositing a first material into a firstdistal end of the columnar pore, and depositing a second material intothe first distal end of the columnar pore. The step of depositing thefirst material includes filling the first distal end of the columnarpore with the first material so that the first material extends to thesecond distal end of the columnar pore along inner walls of the columnarpore. The step of depositing the second material includes filling thefirst distal end of the columnar pore with the second material, so thatthe second material extends to the second distal end of the columnarpore within the first material.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects, details, advantages and modifications of the presentinvention will become apparent from the following detailed descriptionof the embodiments which is to be taken in conjunction with theaccompanying drawings, in which:

FIGS. 1 a and 1 b show a scanning electron micrograph of AAO nanoporearrays, in accordance with an embodiment of the invention.

FIGS. 1 c to 1 e show a formation of ordered arrays of nanopores throughanodic oxidation of aluminum, in accordance with an embodiment of theinvention.

FIG. 2 shows a schematic of a two-terminal electrostatic capacitornanodevice formed within a nanopore, in accordance with an embodiment ofthe invention.

FIG. 3 shows a schematic of a two-terminal electrochemicalsupercapacitor or battery nanodevice formed within a nanopore, inaccordance with an embodiment of the invention.

FIG. 4 shows a schematic of a two-terminal solar cell nanodevice formedwithin a nanopore, in accordance with an embodiment of the invention.

FIG. 5 shows a schematic of a two-terminal nanodevice in which contactsare provided at opposite ends of a nanopore, in accordance with anembodiment of the invention.

FIG. 6 a shows a schematic of a metal-insulator-metal nanocapacitorfabricated by multiple atomic layer deposition steps in anodic oxidealuminum oxide nanopores to form an energy storage structure, inaccordance with an embodiment of the invention.

FIG. 6 b shows a scanning electron micrograph of themetal-insulator-metal nanocapacitor shown in FIG. 6 a, in accordancewith an embodiment of the invention.

FIG. 6 c shows another scanning electron micrograph of themetal-insulator-metal nanocapacitor shown in FIG. 6 a, in accordancewith an embodiment of the invention.

FIG. 6 d shows a schematic of an aggregation of an array ofmetal-insulator-metal nanocapacitors, as shown in FIG. 6 a, to form anenergy storage device, in accordance with an embodiment of theinvention.

FIGS. 7 a and 7 b show a schematic of a two-terminal thermoelectricnanodevice formed within a nanopore, in accordance with an embodiment ofthe invention.

FIG. 7 c shows a schematic of an aggregation of an array ofthermoelectric nanodevices, as shown in FIG. 7 a or 7 b, to form anenergy storage device, in accordance with an embodiment of theinvention.

FIG. 8 shows a schematic of a two-terminal nanodevice array disposed tosense chemicals or biochemicals in gaseous or liquid form, in accordancewith an embodiment of the invention.

FIG. 9 a shows a schematic of a two-terminal electrochemical nanodeviceformed within a nanopore that is compatible with a liquid or aqueouselectrolyte, in accordance with an embodiment of the invention.

FIG. 9 b shows a schematic of an aggregation of an array ofelectrochemical nanodevices, as shown in FIG. 9 a, to form an energystorage device, in accordance with an embodiment of the invention.

FIG. 10 shows a method for creating a vertical two-terminal nanodevice,in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the invention provide two-terminal nanodevice arrays thatutilize nanostructures having nanopores formed by anodic oxidation ofaluminum, and thin films deposited by atomic layer deposition (ALD) andelectrochemical deposition (ECD) to form devices in the nanopores. Thesenanostructures may be coupled to one another to form larger assembliessuitable for power and energy systems.

Certain embodiments of the invention provide two-terminal nanodevicearrays for capture, generation and storage of energy based onmulti-component materials contained within nanoscale pores in aluminumoxide or another dielectric material. A plurality of these nanodevicearrays may be wired in parallel to capture energy from light, eithersolar or ambient, and to generate energy from temperature gradientssensed by thermoelectric devices.

Embodiments of the invention provide electrostatic capacitors,electrochemical capacitors, and batteries for energy storage, wherebydevice layers for energy capture, generation or storage, can be combinedone on top of another or laterally to provide enhanced functionality,including energy and power management systems and electrical powermanagement circuitry with components for capture, generation, storageand distribution.

The two-terminal nanodevices, in accordance with embodiments of theinvention, are formed as nanotubes or nanowires within nanoporesinitially formed as arrays in a nanopore template. Two electricalcontacts can be formed at one end of a nanodevice, whereby one contactis brought to an end of the nanopore where the other contact is formedby a conducting nanotube outside one of the two terminals or by aconducting nanowire inside one of the two terminals. In anotherembodiment, the two electrical contacts can be formed at each end/sideof the nanopore.

Once the two-terminal nanodevice has been fabricated, it may be used asformed in the nanopore as an embedded nanodevice. Alternatively,portions of the two-terminal nanodevice may be exposed by removing aportion of or the entire surrounding nanopore template. Such exposure isimportant, for example, in electrochemical energy storage devices, wherethe two terminals must each be in contact with an electrolyte formedbetween them.

An array of two-terminal nanodevices, in accordance with certainembodiments of the invention, can be employed as electrical energystorage devices, including, for example, electrochemical devices (e.g.,electrochemical supercapacitors, pseudo-capacitors and double-layercapacitors), batteries (e.g., lithium ion batteries), and electrostaticcapacitors. These two-terminal nanodevices can also be used aselectrical energy capture devices functioning as solar cells based oneither semiconducting pn junctions or metal/semiconductor Schottkybarriers.

Further, these two-terminal nanodevices can be used as generators ofthermoelectric energy from temperature gradients between the twoterminals. For example, thermoelectric nanowires or nanotubes areprovided between hot and cold terminals, and the intervening insulatingmaterial is chosen to minimize heat flow between the two terminals, sothat a temperature gradient and thermoelectric voltage are maximized.These thermoelectric nanodevices can be employed as energy capturedevices (i.e., for power generation) or as sensors (i.e., in conjunctionwith bolometers at one terminal to capture infrared images).

According to some embodiments of the invention, the two-terminalnanodevice can be used to perform optical, chemical or sensingfunctions. The pn junction or Schottky barrier configurations, asdiscussed above for solar cells, can be operated as light sources (e.g.,light-emitting diodes or lasers) and/or as optical detectors. Forsensing, the nanodevices may be material layers formed as nanotubesinside nanopores with the two terminals sensing resistance or otherelectrical changes as chemicals introduced into the nanopores chemicallymodify the sensing material or as other environmental changes (e.g.,touch and pressure) modify the surfaces of the sensing material layers.

According to other embodiments of the invention, multilayer types ofnanodevices may be combined into a power management system, includingenergy generation/capture, storage and distribution. These systems mayinclude multiple layers of nanodevice arrays connected in threedimensional configurations.

FIGS. 1 a and 1 b show a scanning electron micrograph of AAO nanoporearrays, in accordance with an embodiment of the invention. Inparticular, FIG. 1 a is a top view and FIG. 1 b is a side view of an AAOnanopore array, in accordance with an embodiment of the invention. Thetops of nanopores 1 each provide access to narrow columns of thenanopores 1 that can include therein high aspect ratio nanoporestructures, or nanodevices. According to embodiments of the invention,the AAO nanopores are narrow (i.e., 5-300 nm in width) and deep (i.e.,50 nm-100 μm), such that their aspect ratio (depth/width) is of order1-1000, and more preferably 50-500. The dimensions of the AAO nanopores1 are based on a choice of electrochemical conditions and sequences usedduring anodization. For example, for nanopores approximately 70 nm indiameter, their center-to-center spacing can be in the order 100 nm.Furthermore, the density of the AAO nanopores 1, for example 10¹⁰pores/cm², can ensure very large active surface areas per unit area.Typically, this area enhancement can be as high as approximately 1000×planar area. Since wet processing can be used, costs associated withvacuum and gas handling technologies can be avoided, and manufacturingcosts can be modest. Thus, AAO can provide a cheap and attractiveplatform for high density nanostructures and devices made from them.

A particular advantage of AAO nanostructures can be that massive arrayscan be fabricated with a high degree of control over their shape andspatial relationship, including their depth, width, and vertical shape(all controlled by anodization conditions). The regularity which resultsis ultimately of major value for manufacturability, providingpredictability for properties for the full array. The nanopore arrayscan have dimensions comparable to that produced by costly, sophisticatedlithography and etching processes in the formation of dynamic randomaccess memory capacitors. However, natural self-assembly from theanodization process itself produces the structures without need for suchcomplex manufacturing steps.

Deposition techniques capable of introducing materials for electricaldevices into very high aspect ratio nanopores are limited. Physicaltechniques, such as evaporation and sputter deposition, cannotsufficiently penetrate deeply into the pores, but chemical methods aresuitable. Electrochemical deposition, carried out in electrolyticsolutions, can successfully cope with the high aspect ratio becauseelectric fields are established between a bottom region of the pore anda counter-electrode removed from the pore in the electrolyte.

FIGS. 1 c to 1 e show a formation of ordered arrays of nanopores throughanodic oxidation of aluminum, in accordance with an embodiment of theinvention. As shown in FIG. 1 c, an anodic oxidization of a substrate 2,for example aluminum, is performed to create AAO 3 with a plurality ofparallel nanopores formed therein, which increasingly order into regulararrangements with uniform dimensions. After the ordering is sufficientlyestablished, the AAO 3 created above the aluminum substrate 2 ischemically removed to leave an aluminum surface having an ordered,patterned array 4 (i.e., a scalloped-shaped structure), as shown in FIG.1 d. With this ordered, patterned array in place, a second anodicoxidation step, as shown in FIG. 1 e, is performed to create a newstructure of AAO 3, which produces a highly ordered, uniform nanoporearray 5 above the aluminum substrate 1.

AAO formation can be carried out using a variety of process parameters,including choice of acid, concentration, voltage, and time. While AAO isthe preferred process and material for very high aspect ratio nanoporearrays, in accordance with embodiments of the invention, a person ofordinary skill in the relevant art will recognize that other materials(e.g., titanium or silicon) can be anodically oxidized to formnanopores. Alternatively, nanopore arrays can be produced by tracketching, in which high energy ions bombard a film (e.g., polymer ormica) to form damage tracks in the material. The damaged material isthen removed by selective etching to form nanopores through it.

The aluminum substrate 2, which is reacted and partially consumed toform the AAO nanopore array 5 can be used in various forms. Aluminumsheets are commercially available which can be used directly. Suchsheets may be anodically bonded to a substrate (e.g., glass), orotherwise attached to a thicker substrate, particularly to facilitatesubsequent processing to form devices, as done in microelectronics. Athin film of aluminum may also be deposited on a substrate (e.g., glassor silicon). The quality of AAO nanopore uniformity and ordering mayvary with the properties of the aluminum (e.g., purity, grain size,etc.). For very high aspect ratio nanopores and ultimately nanodevicesin them, aluminum sheets may be preferred to avoid very long thin filmdeposition times.

According to embodiments of the invention, as will be discussed below,material layers are created within the AAO nanopores to formtwo-terminal nanodevices and arrays thereof. While such nanodevicesinclude multiple material layers created by different depositionprocesses, the preferred processes are limited to those capable ofpenetrating deeply into nanoscale pores. These include, for example, ALDand ECD, as will be discussed in more detail below.

FIG. 2 shows a schematic of a two-terminal electrostatic capacitornanodevice formed within a nanopore, in accordance with an embodiment ofthe invention. As illustrated in FIG. 2, a metal-insulator-metal (MIM)layer structure can be formed in a nanopore in AAO 10. In particular, afirst material 20, as a bottom electrode, can be disposed through afirst distal end of the nanopore 10, extending along the inner walls toa second distal end of the nanopore 10. A second material 30, as a topelectrode, can be disposed through the first distal end of the nanopore10, extending along the inner walls of the first material 20 to thesecond distal end of the nanopore 10. The first material 20 and thesecond material 30 can be concentrically disposed within the nanopore10.

The first material 20 and the second material 30 can be separated by adielectric layer 40, producing an internal electrical field forseparating charges created by light absorption. By suitable patterningof layers on the first distal end of the nanopore 10, a first electricalcontact 50, as a bottom electrode contact, can be formed to provideelectrical current to the first material 20, and a second electricalcontact 60, as a top electrode contact, can be formed on the top surfaceof the AAO nanopore template 10 to provide electrical current to thesecond material 30. As will discussed below, patterning of such contactscan be performed on the scale of one micrometer or larger feature size,realizing lithographic processes and wiring which are routine andinexpensive (i.e., consistent with decades-old microelectronicstechnology). Such patterned wiring allows a massive array of nanodevices(i.e., millions or more) to be wired in parallel to achieve practicalfunctionality for energy storage (i.e., or energy capture).

The electrostatic capacitor nanodevice, as shown in FIG. 2, can alsoinclude a passivation layer 70 formed between the AAO surface and thefirst material 20 to protect the nanodevice from any impurities,defects, or roughness present at the AAO surface. It is known that theAAO process, electrochemical in nature and carried out in complex acidicsolutions, can incorporate impurities from the electrolytic solutioninto the AAO material.

While a variety of processes may be used to create the layers in theelectrostatic capacitor nanodevice shown in FIG. 2, ALD is a preferredmethod to obtain very high aspect ratios. Utilizing alternatingsequences of chemical precursors needed for film growth, ALD exploitsthe self-limiting adsorption/reaction behavior for each precursor pulseto achieve unprecedented control and uniformity of thickness at theatomic level. This enables highly controlled formation of multiplematerial layers, each a few nanometers thick, within narrow AAOnanopores. The control and uniformity achieved in ALD persists even invery high aspect ratio nanopore structures, making ALD nearly ideal as adeposition technique for two-terminal nanodevice fabrication in veryhigh aspect ratio nanopores.

Materials for the first material 20 and the second material 30 can beelectrically conducting so that they can transport charge to and fromtheir surfaces, storing it particularly at their interfaces with thedielectric layer 40 to achieve high power and energy density. Materialsfor the electrodes can include metals, such as aluminum (Al), copper(Cu), tungsten (W), binary compounds, such as titanium nickel (TiN) ortungsten nickel (WN), or more complex materials, such as indium tinoxide (ITO). The materials for the first material 20 and the secondmaterial 30 may be different or the same. The material for thedielectric layer 40 can include aluminum oxide (Al₂O₃) or a high-Kdielectric, silicon dioxide (SiO₂), or other insulating materials. Forthe dielectric layer 40, the material preferably has propertiesincluding high conformality, low leakage current, high breakdown field,and high dielectric constant.

Embodiments of the invention for the electrostatic capacitor nanodevice,as discussed above, provide advantages over conventional electrostaticcapacitors. These advantages arise from the dramatically enhancedsurface area of the first material 20 as a bottom electrode and thesecond material 30 as a top electrode compared to conventional planarstructures. In such devices, energy is stored at electrode surfaces,which for high aspect ratio nanodevices have areas enhanced by 100-300×or more compared to planar capacitor geometries. While these devicesalready feature high power density, their dramatically increased surfacearea enlarges their energy density by corresponding factors.

FIG. 3 shows a schematic of a two-terminal electrochemicalsupercapacitor or battery nanodevice formed within a nanopore, inaccordance with an embodiment of the invention. As illustrated in FIG.3, an electrochemical supercapacitor or battery nanodevice can be formedin a nanopore in AAO 10. A first material 20, as a bottomelectrochemical electrode, can be disposed through a first distal end ofthe nanopore 10, extending along the inner walls to a second distal endof the nanopore 10. A second material 30, as a top electrochemicalelectrode, can be disposed through the first distal end of the nanopore10, extending along the inner walls of the first material 20 to thesecond distal end of the nanopore 10. The first material 20 and thesecond material 30 can be concentrically disposed within the nanopore10.

The first material 20 and the second material 30 can be separated by asolid, gel or polymer electrolyte 42 that can be retained in thestructure under varying conditions of use to achieve supercapacitor orbattery functionality. By suitable patterning of layers on the firstdistal end of the nanopore 10, a first electrical contact 50, as abottom electrode contact, can be formed to provide electrical current tothe first material 20, and a second electrical contact 60, as a topelectrode contact, can be formed on the top surface of the AAO nanoporetemplate 10 to provide electrical current to the second material 30.

The first material 20 as the bottom electrochemical electrode and thesecond material 30 as the top electrochemical electrode are made ofmaterials suitable for ion transport and charge storage. For example,these materials can include metal oxides (e.g., MnO₂, LiMnO₂, CoO₂,V₂O₅, TiO₂, etc.), which are particularly suitable for electrochemicalcapacitors or battery cathodes, as well as carbon, silicon, or otherssuited for battery anodes.

Because the electrochemical electrode materials typically have lowerelectrical conductivity than metal, conducting electrodes, a firstcurrent collecting layer 80 can be formed between the AAO surface andthe first material 20, and similarly a second current collecting layer90 can be formed on an outer surface of the second material 30. Currentcollecting layers 80, 90 are preferably formed from metallic or highlyconducting material, so that electronic charge from the first and secondmaterials 20, 30, as bottom and top electrochemical electrodes, can bereadily transported to and from the first and second electrical contacts50, 60.

Embodiments of the invention for the electrochemical supercapacitor orbattery nanodevice, as discussed above, provide advantages overconventional electrochemical supercapacitors or batteries. Theseadvantages arise primarily in the form of increased power density. Sincecharge is transported and stored in electrochemically active electrodesas ions and atoms, their diffusion in the electrode materials is ratherslow, leading to limitations on how fast charge may be moved, i.e.,reduced power capability. By using very thin layers of electrochemicallyactive electrode materials, ion/atom charge transport times are shorter,resulting in higher power capability.

In accordance with embodiments of the invention, two-terminalnanodevices, such as a two-terminal solar cell nanodevice formed withina nanopore, as shown in FIG. 4, also capture energy. As shown in FIG. 4,the two-terminal solar cell nanodevice includes a first material 20, asa bottom semiconducting electrode, that can be disposed through a firstdistal end of the nanopore 10, extending along the inner walls to asecond distal end of the nanopore 10. A second material 30, as a topsemiconducting electrode, can be disposed through the first distal endof the nanopore 10, extending along the inner walls of the firstmaterial 20 to the second distal end of the nanopore 10. The firstmaterial 20 and the second material 30 can be concentrically disposedwithin the nanopore 10. In the solar cell nanodevice, the first material20 includes a n-type semiconductor material, and the second material 30includes a p-type semiconductor material, or vice versa. The firstmaterial 20 and the second material 30 provide the basic function ofcapturing solar energy and separating electron and hole charge in the pnjunction solar cell nanodevice.

A depletion region 44 is formed at the interface between the twosemiconductor layers, providing an electric field within the depletionregion that separates the electron-hole pair created by photon (light)absorption. By suitable patterning of layers on the first distal end ofthe nanopore 10, a first electrical contact 50, as a bottom electrodecontact, can be formed to provide electrical current to the firstmaterial 20, and a second electrical contact 60, as a top electrodecontact, can be formed on the top surface of the AAO nanopore template10 to provide electrical current to the second material 30.

The solar cell nanodevice can further include a first current collectinglayer 80 formed between the AAO surface and the first material 20, andsimilarly a second current collecting layer 90 formed on an outersurface of the second material 30. First and second electrode currentcollection layers 80, 90 are preferred in many situations to improveefficiency with which electron and hole charge can be transported tofirst and second electrical contacts 50, 60. It should be noted that thesecond (top) electrode current collection layer 90 and the secondelectrical contact 60 should be transparent to solar radiation, enablingit to reach the depletion region 44. A variety of conducting materialssatisfy this requirement, such as indium tin oxide and aluminum zincoxide.

Accordingly, certain embodiments of the present invention can produce afavorable energy capture per unit volume and per unit weight in solarcell devices.

Embodiments of the invention for the solar cell nanodevice, as discussedabove, provide advantages over conventional solar cell nanodevices.Because sunlight penetrates rather deeply into semiconducting materials(i.e., a significant fraction of a micrometer), the solar cellnanodevices, as discussed above, formed in deep (i.e., 1-10 micrometers)nanopores can efficiently absorb much of the solar radiation incidentfrom above. Because the semiconducting layers are thin (i.e., enough tofit within the nanopores), the depletion regions can include asignificant fraction of the layer thickness, so that a large fraction ofelectron-hole pairs created by light absorption can be separated todeliver useful currents. Depletion lengths can be increased by choosinglower doping (i.e., carrier concentration) levels of the semiconductors,while the resulting higher resistance of the semiconductor layers placesa premium on using current collecting layers.

In accordance with another embodiment of the invention, the solar cellnanodevice, as shown in FIG. 4, can be formed as a Schottky barriersolar cell, rather than a pn junction. In this embodiment, one of thefirst material 20 and the second material 30, as semiconducting layers,is replaced by a metal layer, which forms a rectifying Schottky barrierto the other semiconductor layer. Schottky barriers, rather than ohmiccontacts, are typically formed between transition metals and n-typesemiconductors. The Schottky barrier contact to a semiconductor producesa depletion region 44 inside the semiconductor, where electron-holecharge separation can occur, essentially circumventing the need tofabricate two-terminal nanodevices with only one material at each distalend.

In another embodiment of the invention, the two-terminal nanodevicesshown in FIGS. 2-4 may include first and second electrical contacts 50,60 formed at opposite ends of the nanopore 10. For example, FIG. 5 showsa schematic of a two-terminal nanodevice in which contacts are providedat opposite ends of a nanopore, in accordance with an embodiment of theinvention. The two-terminal capacitor nanodevice shown in FIG. 5includes the same general configuration discussed above for theelectrostatic capacitor nanodevice, as shown in FIG. 2, with theexception that the first electrical contact 50 is formed at the seconddistal end of the nanopore 10 (i.e., at the bottom of the nanopore 10),while the second electrical contact 60 is formed at the first distal endof the nanopore 10.

To form the two-sided contact arrangement, as shown in FIG. 5, the firstmaterial 20 must be exposed from the bottom side of the AAO nanopore 10template. This requires removal of the bottom side of the AAO nanopore10 template by wet or dry etching of the aluminum substrate 2 left underthe nanopore 10, as shown in FIG. 1 e, a process that may be done in apattern, so that a mechanical support structure of the remainingaluminum substrate 2 and the AAO 3 layer remain over larger distances.Also, as shown in FIG. 1 e, the AAO 3 layer at the bottom of thenanopore array 5 must be opened by similar etching or otherwise removedby modification of the AAO nanopore fabrication process.

With the first material 20 exposed at the bottom of the nanopore 10template, the first electrical contact 50 can be provided below the AAOnanopore 10 template, as shown in FIG. 5. Depending on the processsequence chosen, the first electrical contact 5 may connect to thebottom of the first material 2 at the level of the bottom surface of theAAO nanopore 10, or it may penetrate into the AAO nanopore 10 to reachthe first material 20 somewhat above the bottom surface of the AAOnanopore 10.

The two-sided contact structure, as shown in FIG. 5, can be achieved forother nanodevices, such as those depicted in FIGS. 2, 3 and 4, asdiscussed above, and in FIGS. 7, 8 and 9 to be discussed below. Havingthe electrical contacts 50, 60 for the two nanodevice terminals atopposite ends of the nanodevice offers advantages over conventionaldevices. For example, these two-terminal nanodevices enable nanodevicedesigns, such as those shown in FIGS. 7, 8 and 9, and provide processvariations that provide a high degree of design flexibility in thestructure of the nanodevices.

One benefit of the two-sided contact structure, in accordance withembodiments of the invention, is that the first electrical contact 50can be provided at the bottom of the unfilled nanopore 10 and used as anelectrode for ECD of materials into the nanopore 10. ECD can be used todeposit a wide range of materials, involves lower cost than ALD, and canbe employed to produce different shapes of the ECD electrode,specifically as nanowires filling the nanopore 10, or as nanotubes fromdeposition against the nanopore 10 sidewall. As ECD begins at theelectrode at the bottom of the open nanopore 10, its height within thepore can be controlled by the process time. Furthermore, multiplematerials can be sequentially deposited or simultaneously co-depositedby ECD, providing a significant flexibility in achieving a variety ofgeometric and compositional shapes.

In this regard, ECD and ALD are complementary in offering designflexibility. While ECD proceeds from an electrode at the bottom of ananopore 10, ALD grows from the top down into the nanopore 10 and doesnot require an electrode. ECD can often fully fill a high aspect rationanopore, but does not achieve highly uniform coverage on nanopore 10sidewalls to the extent that ALD can. While ALD is more often employedto coat the entire surface area of the nanopore 10, precursor dose percycle can be stopped below that needed, resulting in an ALD layer thatcoats the nanopore 10 surface only partway into the nanopore 10. Inthese conditions, suitable modification of ALD and ECD process recipescan provide a large variety of nanodevice design options, includinguniform or graded thickness profiles extending partway or fully fromeither end of the nanopore 10.

FIG. 6 a shows a schematic of a metal-insulator-metal nanocapacitorfabricated by multiple atomic layer deposition steps in anodic oxidealuminum oxide nanopores to form an energy storage structure, inaccordance with an embodiment of the invention. FIGS. 6 b and 6 c showscanning electron micrographs of the metal-insulator-metal nanocapacitorshown in FIG. 6 a, in accordance with an embodiment of the invention.

As shown in FIG. 6 a, anodic oxidation of aluminum 2 leads to formationof AAO 3 with deep pores on whose surfaces a sequence of ALD layers canbe deposited to create a MIM device structure, as shown in FIGS. 2-4.The detailed structure of MIM layers is seen by scanning electronmicroscopy in FIGS. 6 b and 6 c for regions at the top and bottom of thenanopores 10, respectively. In this particular example, the porediameter was 60 nm, the bottom TiN electrode thickness was 5.6 nm, theAAO dielectric thickness was 6.6 nm, and the top TiN electrode thicknesswas 12.6 nm, nearly filling the nanopore 10. It should be noted thatlayer thicknesses could be readily adjusted to fully fill the nanoporeor instead to leave internal volume. The pore depth for the structuresshown in FIGS. 6 a, 6 b and 6 c was 1 micrometer.

Embodiments of the invention further provide MIM nanocapacitor arraysfor both 1 and 10 μm depths, forming capacitors whose macroscopicexternal contacts to the TiN ALD layers in the MIM structure were madeabove the nanopores 10 and to the underlying aluminum 1 below thenanopores 10. For example, capacitors with 0.01267 mm² area (e.g., about0.1 mm in diameter) connected approximately 10⁶ nanocapacitorstructures, like those shown in FIGS. 6 a, 6 b and 6 c, in parallel andindicated capacitance densities of about 10 and 100 μF/cm²,respectively. This corresponds to an energy density of order 0.7 W-h/kg,placing the performance of these devices well above the energy densityof conventional electrostatic capacitors, while retaining comparablepower. These nanodevices also provide energy density values that exceedthose achieved using all prior microstructure and nanostructureapproaches.

FIG. 6 d shows a schematic of an aggregation of an array ofmetal-insulator-metal nanocapacitors, as shown in FIG. 6 a, to form anenergy storage device, in accordance with an embodiment of theinvention. As shown in the scanning electron microscopy of FIG. 6 b, MIMtrilayer structures from one nanodevice can connect continuously to eachother over the top of the AAO material between nanopores. This meansthat a massive array, (i.e., billions of nanodevices over a few squareinch area) are already connected in parallel. To define a suitable setof useful devices, this massive array is then partitioned into smallerdevices for testing and use in energy applications, as will be discussedbelow.

For example, the electrostatic capacitor nanodevices, as shown in FIGS.6 a to 6 c within a 125 micrometer diameter region may be wired inparallel to form an aggregate capacitor microdevice. The wiring schemeto create small capacitors is shown in FIG. 6 d. As shown in FIG. 6 d, afirst electrical contact 50 is formed to the first material 20, as acommon bottom electrode, of all the nanocapacitors, which are alreadywired together by their shared ALD bottom electrode layer. Furthermore,by patterning a second electrical contact 60 as a small dot (i.e., witha 125 micrometer diameter), this electrical contact connects only to thenanodevices underneath it, including about one million nanocapacitors(i.e., the MIM electrostatic nanocapacitor shown in FIG. 2). Theresulting electrostatic capacitor, composed of a million nanodevices,can then be charged, discharged, tested and used by their first andsecond electrical contacts 50, 60. Over a massive array of suchnanodevices, covering inches or more, many such capacitors can be madeand further interconnected to form an electrostatic energy storagesystem.

This aggregation of nanodevices, accomplished with simple lithographicpatterning of wires, is characteristic of how nanodevices and massivearrays made from them are used in accordance with embodiments of theinvention. The extent of aggregation used to form such arrays, each ofwhich may be regarded as analogous to a “chip”, depends on a variety ofperformance metrics sought, capabilities of the specific process andnanodevice technology, and regard for testability, yield andreliability. In turn, for massive levels of integration, themicrodevices may be wired together to create systems, for example, onthe scale of solar panels of order 1 meter in size. Analogousconsiderations for how this “macro” wiring is designed apply asidentified for the microdevice level, as well as how many levels ofaggregation and global wiring are used.

FIGS. 7 a and 7 b show a schematic of a two-terminal thermoelectricnanodevice formed within a nanopore, in accordance with an embodiment ofthe invention. The two-terminal thermoelectric nanodevice, as shown inFIGS. 7 a and 7 b, use a two-sided contact configuration, as shown inFIG. 5, and discussed above.

Electrical energy can be extracted from a thermoelectric material (e.g.,bismuth telluride), when a temperature gradient exists between twopositions in the material. As shown in FIGS. 7 a and 7 b, athermoelectric material 100 is formed as a nanotube or a nanowire withina nanopore 10. The nanopore 10 initially includes AAO material (note:aluminum oxide has a low thermal conductivity). Metal contacts 110, 120at the top and the bottom of the nanopore are connected electrically tothe thermoelectric nanotube or nanowire 100. If the top metal contactlayer 110 is placed in thermal contact with a gas, liquid or solid atelevated temperature T1, while the bottom metal contact layer 120remains at a lower temperature T2, a voltage is generated between themetal contacts 110, 120 to generate power. Once formed, the AAO materialmay be removed in some locations, or replaced by another insulatingmaterial with an even lower thermal conductivity, so that higher thermalgradients and thermoelectric power can be attained.

These thermoelectric nanodevices, as shown in FIGS. 7 a and 7 b, may bearranged in an array, as shown in FIG. 7 c. FIG. 7 c shows a schematicof an aggregation of an array of thermoelectric nanodevices, as shown inFIG. 7 a or 7 b, to form an energy storage device, in accordance with anembodiment of the invention. A thermoelectric energy harvesting system,as shown in FIG. 7 c, may be employed, for example, to harness excessheat from an engine by contacting the metal contact layer 110 to theengine, while keeping metal contact layer 120 cooled to a lower, ambienttemperature (i.e., with air cooling). A low thermal conductivityinsulator 130 (e.g., AAO, polymer, porous or air) may be formed at theends of the thermoelectric energy storage device to insulate energy fromescaping the sides of the device.

Thus, in accordance with an embodiment of the invention, a two-terminalthermoelectric nanodevice can serve as the basis for other applications,such as a thermoelectric imaging device. In this case the top metalcontact layer 110 can be patterned to form an array of pixels, withimage information read out as voltages of the top electrode pixels incomparison to the voltage at the bottom metal contact layer 120. Thepixels may be coated by other material to optimize absorption andconsequent heating by the radiation, as in an infrared imagingapplication.

In accordance with another embodiment of the invention, an analogousapplication involves use of piezoelectric material instead ofthermoelectric material in a two-terminal nanodevice configuredsimilarly to the nanodevice shown in FIG. 7 c. Mechanical forces appliedbetween the top metal contact 110 and the bottom metal contact 120layers will generate electrical voltages between these layers if theyare connected by piezoelectric nanotubes or nanowires, for example toharvest mechanical energy from vibration or pressure as electricalenergy.

FIG. 8 shows a schematic of a two-terminal nanodevice array disposed tosense chemicals or biochemicals in gaseous or liquid form, in accordancewith an embodiment of the invention. As shown in FIG. 8, a sensormaterial is deposited as nanotubes inside the nanopores. In thin filmform, these materials (e.g., tin oxide) have properties that exhibitresistivity changes upon exposure to chemicals (e.g., organic vapors,such as alcohols).

According to an embodiment of the invention, this two-terminalnanodevice array, as shown in FIG. 8, is formed by coating a nanopore 10and perhaps other surfaces of an AAO membrane 3 with chemical sensingfilms 140. Metal contacts 50 and 60 are formed at opposite ends of thenanopores to measure resistance of the sensor films during exposure toanalytes in gaseous or liquid form. The metal contact structures 50, 60are shaped such that they do not substantially cover or close thenanopore regions at either end, allowing gas or liquid flow through thenanopores. By sealing the sensing array to a sealing structure 150,which separates a higher pressure chamber 160 from a lower pressurechamber 170 in a pressure controlled vessel 180, gas or liquid from theformer is forced to flow through the nanopores 10. As adsorption,absorption, or reaction of species from the gasous or liquid analytehappens on the sensor material 140, resistance change is measure betweenmetal contacts 50, 60.

While the electrochemical nanodevice, as shown in FIG. 3, is nominallyrestricted to use of electrolytes in solid, gel or polymer form, thetwo-terminal electrochemical nanodevice, as shown in FIG. 9 a, iscompatible with liquid electrolytes. Either aqueous or organic, liquidelectrolytes are by far the most common in battery and supercapacitorsystems. In this case, current collecting layers and electrochemicalmaterials together form electrodes at each end of AAO nanopores, with aseparation region 150 between them where no material is deposited on topof the insulating sidewall of the AAO nanopore. The energy storagedevice, as shown in FIG. 9 b, includes a cell 160 composed of ananodevice array that includes a plurality of two-terminalelectrochemical nanodevices, as shown in FIG. 9 a, configured as a topcell electrode 170 and a bottom cell electrode 180. The energy storagedevice further includes a top wiring contact 190 and a bottom wiringcontact 200.

In accordance with an embodiment of the invention, this structure isformed using ALD for its ability to deposit into high aspect rationanopores, while limiting penetration by judicious choice of precursordose per cycle, as stated above. A representative process sequence tofabricate the electrochemical nanodevice array shown in FIGS. 9 a and 9b is as follows. First, a top contact wiring pattern is formed on top ofthe AAO membrane to provide structural rigidity for the membrane. ThenALD is used to deposit a current collecting layer part way into the topof the nanopores, followed by ALD and/or ECD to deposit theelectrochemically active charge storage material (e.g., metal oxide)over the current collecting layer. This forms a top nanoelectrode array.The underlying aluminum and AAO material on the bottom side are thenpatterned and etched to expose the bottom of the nanopores in apatterned region. A bottom nanoelectrode array is then formed from theexposed bottom opening of the nanopores, using ALD and/or ECD as for thetop nanoelectrodes. With each nanopore in the active region nowcontaining a top and bottom nanoelectrode separated by a distance thatis a fraction of the nanopore length, the entire structure is immersedin liquid electrolyte, thus activating its function as anelectrochemical energy storage device.

The two-terminal nanodevices, as discussed above reflect both energystorage and capture. According to embodiments of the invention, thenanodevices, as discussed above, can be combined to form multilayernanodevice arrays vertically stacked or horizontally located. Hybridsystems capable of both storage and capture are highly desirable forapplications of renewable sources (e.g., storing solar energy capturedduring daytime for use at night), as well as for other hybrid energysystems (e.g., high power supercapacitors and high energy batteries). Insuch cases, power management is essential and best integrated on thesame nanodevice technology platform. The nanodevices discussed above canserve as power management components as well. Conducting nanowires canbe circuit connections (or in proper geometry as inductors),electrostatic capacitors can serve as storage elements, pn junctions canperform as diodes, and Schottky barrier junctions as Schottky or ohmiccontacts. The solar cell nanodevices can also function as lightdetectors or light emitting diodes for optoelectronic functionality.

FIG. 10 shows a series of steps for a process for creating a verticaltwo-terminal nanotube device, in accordance with an embodiment of theinvention.

As discussed above, an ordered array of nanopores 10 in an aluminumlayer can be formed using the process shown in FIGS. 1 c-1 e (step 200).According to an embodiment of the invention, as shown in FIG. 10, afirst material 20 is deposited into an AAO nanopore 10 using a sequenceof ALD deposition steps. The first material 20 is deposited into a firstdistal end of the nanopore 10, so that it extends toward a second distalend of the nanopore 10 along inner walls of the nanopore 10 (step 210).A second material 30 is deposited into the first distal end of thenanopore 10, so that it extends toward the second distal end of thenanopore 10 within the first material 20 (step 220).

The method includes depositing a third material into the first distalend of the nanopore 10, so that it extends toward the second distal endof the nanopore 10 between the first material 20 and the second material30 (step 230). As will be understood by a person of ordinary skill inthe relevant art, the third material is deposited during the sequentialdeposit of the first and second material, so that the first material isdeposited, followed by the third material and then the second material.In accordance with some embodiments, the third material may include oneof an electrical insulator and an electrolyte. Whereas, in otherembodiments, the third material may not be needed, for example, in thecase where a plurality of sequentially formed layers are deposited toform the nanodevice.

The method includes disposing and connecting a first wiring material 50to an exposed end of the first material 20, and disposing and connectinga second wiring material 60 to an exposed end of the second material 30(step 240). The first wiring material 50 and the second wiring materialmay both be connected on a top surface of the nanopore 10, or may beconnected on a top surface and a bottom surface of the nanopore 10,respectively. The method of connecting the first wiring material 50 andthe second wiring material 60 may include connecting a plurality ofnanopores 10 in parallel.

Either the first or second materials 20, 30 can be replaced with two ormore materials to achieve different device behavior and performance. Forexample, different materials can be used to create the electrostaticcapacitor nanodevice, shown in FIG. 2, and different materials can beused to create the electrochemical nanodevice, shown in FIG. 3.

While high conformality and control of ALD makes it attractive forforming first and second materials 20, 30 in the AAO nanopores 10, otherprocesses, such as ECD, CVD, and sol-gel processes can be useful forsome of the process steps to introduce materials into the nanopores 10.

The choice of materials and deposition processes can dependsignificantly on the device type to be created. For the two-terminalnanotube capacitor nanodevice, as shown in FIG. 2, ALD is a preferreddeposition process for introducing the first and second materials 20,30, in order to achieve uniform deposition within the nanopore 10.Whereas, a conventional physical vapor deposition (e.g., evaporation orsputtering) may be a preferred process to deposit the first and secondwiring materials 50, 60, to electrically connect a massive array ofnanodevices

For the electrochemical nanodevice, as shown in FIG. 3, ECD may be apreferred process to deposit the first material 20 if a currentcollecting layer is already in place and can be contacted to define itsvoltage during ECD of the first material 20, as a bottom electrode. Ifinorganic, the electrolyte layer 42, as shown in FIG. 3, may bedeposited by sol-gel processes and by ALD. ALD processes are also knownfor some polymer systems that could include a polymer electrolyte.

Various electron donor and acceptor materials can be chosen for thefirst and second semiconductor materials 20, 30. Either donor oracceptor material, or n-type or p-type semiconductor material, can bechosen as the first material, to be deposited by ALD as a first materialin a first distal end of each nanopore. Semiconducting materials can be,for example, zinc oxide (ZnO) (either n-type or p-type), titanium oxide(TiO₂) (n-type), copper oxide-nickel oxide (Cu₂O—NiO) (p-type), andvanadium oxide (V₂O₅).

It is to be understood that in an embodiment of the present invention,the steps are performed in the sequence and manner as shown although theorder of some steps and the like can be changed without departing fromthe spirit and scope of the present invention. In addition, the processsequence described in FIG. 10 can be repeated as many times as needed.Variations of the process sequence described in FIG. 10 can also usedifferent materials and processes.

The many features of the invention are apparent from the detailedspecification and, thus, it is intended by the appended claims to coverall such features of the invention which fall within the true spirit andscope of the invention. Further, since numerous modifications andchanges will readily occur to a person of ordinary skill in the relevantart, it is not desired to limit the invention to the exact constructionand operation illustrated and described, and accordingly all suitablemodifications and equivalents can be resorted to, falling within thescope of the invention.

We claim:
 1. A vertical nanotube device, comprising: a nanotube column disposed in an anodic oxide material extending from a first distal end of the anodic oxide material to a second distal end of the anodic oxide material; a first material disposed inside the column; a second material disposed inside the column; and a third material disposed between the first material and the second material, wherein the first material fills the first distal end of the column and extends to the second distal end of the column along inner walls of the column, wherein the second material fills the first distal end of the column and extends to the second distal end of the column within the first material, wherein both the first material and the second material are exposed at opposite distal ends of the column, and wherein the vertical nanotube device is perpendicular or substantially perpendicular to a substrate of the vertical nanotube device.
 2. A vertical nanotube device, comprising: a column disposed in an anodic oxide material extending from a first distal end of the anodic oxide material to a second distal end of the anodic oxide material; a first material disposed within the column; a second material disposed within the column; and a third material disposed between the first material and the second material, wherein the first material fills the first distal end of the column and extends to the second distal end of the column along inner walls of the column, wherein the second material fills the first distal end of the column and extends to the second distal end of the column within the first material, wherein both the first material and the second material are exposed at opposite distal ends of the column, wherein the vertical nanotube device is perpendicular or substantially perpendicular to a substrate of the vertical nanotube device, and wherein the first material and the second material are concentrically disposed within the column.
 3. The vertical nanotube device of claim 1, further comprising: a first wiring structure operatively connected to an exposed end of the first material; and a second wiring structure operatively connected to an exposed end of the second material, wherein the first and the second wiring structures are configured on a top surface of the column.
 4. A vertical nanotube device, comprising: a column disposed in an anodic oxide material extending from a first distal end of the anodic oxide material to a second distal end of the anodic oxide material; a first material disposed within the column; a second material disposed within the column; and a third material disposed between the first material and the second material, wherein the first material fills the first distal end of the column and extends to the second distal end of the column along inner walls of the column, wherein the second material fills the first distal end of the column and extends to the second distal end of the column within the first material, wherein both the first material and the second material are exposed at opposite distal ends of the column, wherein the vertical nanotube device is perpendicular or substantially perpendicular to a substrate of the vertical nanotube device, and wherein the third material comprises one of an electrical insulator and an electrolyte.
 5. The vertical nanotube device of claim 1, wherein the vertical nanotube device comprises one of an electrostatic capacitor, a battery, a supercapacitor, a solar cell, a light emitting diode and a laser.
 6. The vertical nanotube device of claim 1, wherein the first material and the second material are electrically conducting.
 7. The vertical nanotube device of claim 1, wherein one of the first material and the second material comprises an electron donating material, and wherein the other of the first material and the second material comprises an electron accepting material.
 8. The vertical nanotube device of claim 1, wherein the anodic oxide material is selected from the group consisting of aluminum oxide, titanium oxide, silicon, or a dielectric material.
 9. The vertical nanotube device of claim 1, further comprising: a passivation layer disposed on a surface between the anodic oxide material and the first material.
 10. The vertical nanotube device of claim 1, further comprising: a first conductive layer disposed between the anodic oxide material and the first material; and a second conductive layer disposed on an outer surface of the second material.
 11. The vertical nanotube device of claim 10, wherein the first conductive layer and the second conductive layer each comprise a material selected from the group consisting of a metal or a conducting compound.
 12. A vertical nanotube device, comprising: a column disposed in an anodic oxide material extending from a first distal end of the anodic oxide material to a second distal end of the anodic oxide material; a first material disposed within the column; a second material disposed within the column; and a third material disposed between the first material and the second material, wherein the first material fills the first distal end of the column and extends to the second distal end of the column along inner walls of the column, wherein the second material fills the first distal end of the column and extends to the second distal end of the column within the first material, wherein both the first material and the second material are exposed at opposite distal ends of the column, wherein the vertical nanotube device is perpendicular or substantially perpendicular to a substrate of the vertical nanotube device, and wherein one of the first material and the second material comprises an n-type semiconductor material, and wherein the other of the first material and the second material comprises a p-type semiconductor material.
 13. The vertical nanotube device of claim 1, wherein the anodic oxide material comprises a rectangular patterned area disposed on the substrate.
 14. The vertical nanotube device of claim 4, wherein the electrolyte comprises one of a solid, gel or polymer electrolyte.
 15. The vertical nanotube device of claim 4, wherein the first material and the second material each comprise a material selected from the group consisting of a metal oxide, carbon and silicon.
 16. The vertical nanotube device of claim 1, wherein one of the first material and the second material comprises a metal layer, and wherein the other of the first material and the second material comprises a semiconductor material.
 17. The vertical nanotube device of claim 16, wherein the vertical nanotube device comprises a Schottky barrier. 